Furnace seal

ABSTRACT

A SEALING SYSTEM FOR A FURNACE, SUCH AS A CONTINUOUS BAR ANNEALING FURNACE HAVING A PLURALITY OF SEALING ELEMENTS SUPPORTED ACROSS THE OPENING TO THE FURNACE IN A SIDE-BY-SIDE RELATIONSHIP. EACH ELEMENT OF THE SEAL HAS TWO PARALLEL PLANAR SIDES IN ALIGNMENT WITH THE DIRECTION OF ENTRY INTO THE FURNACE. MATERIAL ENTERING THE FURNACE CONTACTS ONE OR MORE ELEMENTS CAUSING THEM TO BE DISPLACED, PERMITTING THE MATERIAL TO ENTER THE FURNACE. THE DIMENSION OF THE PLANAR SIDES OF EACH ELEMENT IS IN DIRECTION OF DISPLACEMENT IS OF SUCH MAGNITUDE THAT THE SIDE OF ONE ELEMENT REMAINS IN A CONTINUALLY OVERLAPPING RELATIONSHIP WITH THE SIDE OF AN ADJACENT ELEMENT WHEN ONE OF THE ELEMENTS IS DISPLACED BY THE MATERIAL ENTERING THE FURNACE.

Se t, 20, 1971 Filed Feb. 2. 1970 w. M. BLOOM FURNACE SEAL 3 Sheets-Sheet l Ilrllllll;

INVENTOR. WILLIAM M. BLOOM At funny W. M. BLOOM FURNACE SEAL Sept. 20, 1971 5 Sheets-Sheet 2 Filed Feb. 2, 1970 A ME Attorney Sept. 20, 19 71 W. M. BLOOM 3,505,288

FURNACE SEAL Filed Feb; 2. 1970 3 Sheets-Sheet 8 INVENTOR.

WILLIAM M. BLOOM ZAM/F Attorney United States Patent Office 3,606,288 Patented Sept. 20, 1971 3,606,288 FURNACE SEAL William M. Bloom, Pittsburgh, Pa., assignor to Allegheny Ludlum Steel Corporation, Pittsburgh, Pa. Filed Feb. 2, 1970, Ser. No. 7,721 Int. Cl. C21d 1/00 US. Cl. 2665R Claims ABSTRACT OF THE DISCLOSURE A sealing system for a furnace, such as a continuous bar annealing furnace having a plurality of sealing elements supported across the opening to the furnace in a side-by-side relationship. Each element of the seal has two parallel planar sides in alignment with the direction of entry into the furnace. Material entering the furnace contacts one or more elements causing them to be displaced, permitting the material to enter the furnace. The dimension of the planar sides of each element in the direction of displacement is of such magnitude that the side of one element remains in a continually overlapping relationship with the side of anadjacent element when one of the elements is displaced by the material entering the furnace.

BACKGROUND OF THE INVENTION The purpose of this invention is to provide an effective atmosphere seal at the entry or exit ends of a chamber, partigularly one having an internal atmosphere different than that of the environment of the furnace, such as a continuous bar annealing furnace having a hydrogen atmosphere.

Continuous roller-hearth, atmosphere-type, tool steel bar annealing furnaces are designed to provide close temperature and atmosphere controls, so that as the temperature of charge material is increased or decreased within the furnace, the composition of the atmosphere may be changed to maintain an atmosphere neutral to the carbon content of the steel. In this manner the carbon content of the annealed bar after the annealing will be substantially equivalent to its carbon content before the anneal. Endothermic and exothermic gases are continuously admitted to the furnace at various predetermined points along its length in metallurgically prescribed quantities and ratios, to obtain the desired variation in atmosphere gas .composition and temperature. Because it may be desirable to have a gas mixture injected into the furnace at a given point flow towards the exit end for one cycle and" product and more towards the entry end for another product, means to bias the quantity of gas flowing out of one end of the furnace over the other end of the furnace is required.

The means to control the quantity of gas flow out of the furnace ends should be able to maintain a controlled atmosphere gas flow rate under varying environmental conditions such as when the conditions at the furnace ends vary, or the bar load passing through the furnace ends varies the cross-sectional area of the seal. Positive internal furnace pressure greater than environmental pressure is required in isolated atmosphere furnaces, such as at a sealing chamber to prevent infiltration of the environment atmosphere through the seals and into the furnace, causing a contamination of the atmosphere therein. This internal furnace pressure acting across the seals must also be great enough to overcome the external air impingement of the environmental disturbances in the vicinity of the furnace, such as the opening of building doors, etc. The effectiveness of the seals and the quantity of furnace atmosphere gas requirements to maintain a positive pressure within the furnace are dependent upon the seals gas flow resistance, determined by the cross-sectional flow area, the flow area shape for flow coefficient, and the length of flow path for frictional factors. An effective seal design should minimize gas leakage through the seals by providing suflicient flow resistance under all conditions of operation, to maintain a continuing, but minimized flow of atmosphere from the furnace to the environment outside. Thus, the seal should have sufficient flow resistance to make any influence of external environment atmosphere disturbance on the seals negligible, both when the seals are in the closed position as well as the open position as during the charging of the furnace.

Conventional seals used to restrict the flow of atmosphere gases from a continuous furnace consist of a plurality of sheet-like flapper baffles hung across the furnace opening width. Usually two or more rows of baffles are hung to increase the flow resistance to a workable level. These bafiles are somewhat effective in reducing the size of the opening to the general shape of the load crosssection, but have a major deficiency in that side holes are opened up between an open or partially open flapper and an adjacent closed flapper when material passes through. This opening may vary from several to as much as 50 square inches for a 2-inch flap extending over a vertical opening of 12 inches or greater in area, dependent upon the dimension of seal height. This open area, or side hole, enables substantially large quantities of furnace atmosphere to escape, thereby requiring large quantities of atmosphere make-up cast to retain the desired furnace pressure. Further, due to the side holes the flow rate of atmosphere at the seals varies substantially with changes in the seal cross-section contour between the no load condition and the loaded condition thus, varying the internal bias furnace atmosphere points. The conventional baffle seals are also substantially influenced by abrupt changes in external environment atmosphere such that the flow rate of furnace atmosphere across the seal varies, affecting the atmosphere profile within the furnace. Disturbing the atmosphere profile within the furnace causes mixing and a more homogeneous mixture of gases in the different section. The quality of many annealing processes is directly dependent upon the attainment of a definite, tapered, reproducible furnace atmosphere composition along furnace length. Thus, the furnace atmosphere disturbances allowed by conventional seals materially affect the desired furnace atmosphere profile and quality of the anneal. The seals of my invention enable the establishment of a sub stantially continuous atmosphere gas flow rate across them to the external atmosphere which is relatively unaffected by the entrance or exiting of material or various external wind effects. Thus, the utilization of my seals permits the establishment of a stable, profiled atmosphere along the furnace length, enabling the production of a uniform, high quality anneal.

SUMMARY OF THE INVENTION A seal for a chamber such as an isolated atmosphere furnace having a plurality of elements in a side-by-side relationship, each element having two substantially parallel sides and joined by a separator extending therebetween. The individual elements are supported across the opening to said chamber and adapted to be individually displaced by a workpiece entering therein. The dimensions of said parallel sides are of predetermined width such that adjacent sides of elements maintain a continually overlapping relationship when an element is displaced by an entering workpiece.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of the seals of my invention as embodied in a continuous bar annealing furnace shown in cross section.

FIG. 2 is a front elevation of the structure of FIG. 1.

FIG. 3 is a side elevation of a seal element of my invention.

FIG. 4 is a view looking in the direction of arrows IVIV of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and FIGS. 1 and 2 in particular, reference numeral 2 indicates the entry portion of a furnace, such as a continuous bar annealing furnace, having an entry vestibule 4 separated from the furnace proper 6 by means such as a heat shield 8. The entry vestibule 4 of the annealing furnace has a gas-tight envelope 10 supported by structure 12. conventionally, bafiles 14 are suspended from the overhead portion of the vestibule, being usually an alloy sheet welded in a gas-tight manner to the overhead of envelope 10. At these baffles 14, supporting rods 15 extend across the vestibule 4, carrying sealing curtains 16, composed of individual sealing elements 18, such as those of my invention and later described. Though three baffies 14, rods 15, and curtains 16 are illustrated, the number for any particular furnace vestibule may vary and will be determined by the various operating parameters, namely the temperatures, gases, and pressures involved therein. Vestibule 4 is further provided with rolls 20 supported by the furnace structure in a manner well known in the art for supporting and conveying a workpiece W such as a bar of steel to be annealed.

Referring now to FIGS. 3 and 4, seal element 18 has two parallel planar sides 22 which are separated and supported by partition 24. In the preferred embodiment herein disclosed, partition 24 forms a third side which, when the element 18 is hung within the vestibule 4, faces the approaching workpiece W. Element 18 is adapted with means 26 to mount the element on the rods 15. In the preferred embodiment disclosed, the mounting means 26 is a sleeve 28 attached to both the sides 22 and partition 24, forming a gas-tight jointure therewith which enables the element to be rotated as illustrated in FIG. 1 at 30 when workpiece W enters the vestibule 4. Sides 22 of element 18 are further adapted to be triangular in shape and oriented such that their lateral dimension continually increases away from the mounting means 26 toward end 32. The dimension of end 32 is predetermined to be greater than the vertical displacement of element 18 upon the entry of workpiece W, to insure a continually overlapping relationship of the adjacent sides 22, as illustrated at 34 of FIG. 1. In the preferred embodiment element 18 is further adapted so that edge 32 presents a sloping aspect to the retreating workpiece passing the element 18-.

In this embodiment the seals of this invention are mounted in rows along the baffle 14 being suspended from the transverse rod 15 forming a series of articulating sealing baffie-like elements. The individual elements 18 swing upward to a position as at 30, being displaced by the workpiece W passing into the furnace vestibule 4, on rollers 20. Elements 1-8 in the preferred embodiment are hung to form an angle A when closed, offset from the vertical plane in the direction of bar travel. Such an angle permits a tight closer of the element 18 of the edge of side 24 against sealing means as plate 38. The offset hanging of element 18 also prevents wedging or lock-up of the element against the bottom sealing means which might otherwise happen if the element were allowed to swing approximately to the vertical position upon passage of the workpiece W. The offset hang-ing of the element 18 also reduces the area above the element required for the .full displacement of the element 18 upon the passage of a workpiece W. As may be seen in FIG. 1, sides 22 have sufficient lateral dimension to form a continuous overlapping relationship as at 34 between the closed and opened adjacent elements.

As previously discussed, the trailing edge 32 of each element in the preferred embodiment presents a sloping aspect to the passing workpiece W. By such structure, end 32 slides down to the end of the workpiece W as it moves past, thereby eliminating element 18 dropping to a closure and abrupt impact of the seal edge 32 against the sealing plate 38 upon closure. Additional advantage is gained from the overlapping relationship of the adjacent elements in that maintaining the overlap significantly, as illustrated at 34 increases the flow resistance to the atmosphere gases within the furnace and vestibule, thereby reducing the intensity from the gases to evacuate the chambers. In the preferred embodiment, the overlap measures 1 /2" for a clearance of ,4 over a length of 18 /2" on side 22. In the described embodiment these dimension parameters provide additional preferred advantage in that the gas flow betweenelements in the overlap area is turbulent as opposed to laminar according to Reynolds criterion. By causing the gas flow to go turbulent, additional gas flow resistance is developed across the seal area further enhancing the seal effectiveness and the stability of the tapered furnace atmosphere.

In preferred installations the sealing elements would be installed in curtains 16 at both the entry and discharge ends of vestibule 4 and furnace 6, either singly or in multiple rows. Ideally, the lateral dimension of the individual element 18 formed by the distance between the sides 22 by partition 24 would be slightly larger than the width of the workpiece W passing into the furnace. The elements of the illustrated installation measure 2 inches and accommodate bars of slightly less width. Charge material may also be bundled to a width closely approaching an integral multiple of element width. In actual practice, the seals have worked effectively for coiled material displacing several seal elements upon entry into the furnaces.

In the embodiment disclosed, lift plates 40 affixed to shaft 15 and operable upon rotation of shaft 15 by crank 42, are positioned against element 1 8 when in a closed position. Rotation of crank 42 and shaft 15 will lift all elements 18, thus raising the curtain 16 and presenting up to a full opening to furnace vestibule 4 for those instances where decreased gas flow resistance or access is desired. In the preferred embodiment disclosed, rod 15 is hollow and water cooled to maintain the shaft strength at the elevated temperatures encountered within the vestibule 4.

I claim:

1. Apparatus for sealing an opening in a closed atmosphere chamber comprising: a plurality of individual elements having two parallel planar sides; a separator disposed between said planar sides joined thereto and having a dimension along said jointures at least as large as one dimension of said opening; mounting means adapting said elements for displacement in the direction of said two planar sides, said two sides having a dimension in the direction of displacement at least as large as said displacement and said individual elements being mounted in a side-by-side relationship having a planar side of one in juxtaposed relationship with the planar side of an adjacent element whereby said juxtaposed planar sides of adjacent elements maintain a continually overlapping relationship when one of said elements is displaced.

2. Apparatus according to claim 1 wherein any atmosphere flow exiting said chamber between adjacent elements is turbulent flow.

3. Apparatus according to claim 2 wherein the chamber is an annealing furnace and said mounting means adapting said elements for displacement in the direction of said planar sides includes pivotal mounting means whereby said displacement is rotational about said pivotal mounting means in the direction of said planar sides.

4. Apparatus according to claim 3 wherein said planar sides are substantially triangular in shape with said pivotal mounting means disposed at one corner of said triangle.

5. Apparatus according to claim 4 wherein said separator is joined to said pivotal mounting means forming a gas-tight juncture therewith and extends between the said planar sides along a corresponding edge of said triangular sides forming a gas-tight juncture therewith.

6. Apparatus according to claim 5 wherein said individual elements are adapted to be displaced by a workpiece progressing through said furnace.

7. An apparatus according to claim 6 wherein the width of an individual element is larger than the width of the workpiece progressing through said furnace whereby said workpiece when aligned with said individual elements will displace only one element per row.

8. Apparatus according to claim 7 wherein said individual elements are adapted with means displacing all elements upon actuation of said means.

9. Apparatus according to claim 8 wherein said elements are disposed in a plurality of rows.

References Cited UNITED STATES PATENTS 2,233,474 3/1941 Dreffein 2665R 3,105,863 10/1963 Holcroft et al. 2665R 3,130,250 4/1964 Mescher 2665R GERALD A. DOST, Primary Examiner US. Cl. X.R. 2665A 

